Modeling of bicarbonate within the dialysate fluid, specifically a lower than standard concentration has been suggested in facilitating the removal of phosphate and potassium. To test this hypothesis, the study will use a cross-over study design to evaluate phosphate and potassium removal during dialysis by altering bicarbonate concentration in dialysis fluid (i.e. high bicarbonate, standard bicarbonate washout, low bicarbonate), and compare the effects of the different dialysate bicarbonate concentrations on the removal of phosphate and potassium during hemodialysis